Investigators have located a surveillance camera that shows people who are now wanted for questioning, Chicago police spokesman Anthony Guglielmi said in a statement on Twitter. Detectives had not yet found still images or video of the actual incident as of late Tuesday evening, police told CNN.

Photos of people of interest who were in area of the alleged assault & battery of Empire cast member. While video does not capture an encounter, detectives are taking this development seriously & wish to question individuals as more cameras are being reviewed pic.twitter.com/xJDDygtocr

Smollett said he was attacked in the early morning hours on Tuesday in a Chicago neighborhood known as Streeterville by two people who were “yelling out racial and homophobic slurs” and “poured an unknown chemical substance on the victim,” according to police.

Investigators are testing the chemical Smollett said he was doused with and have yet to confirm the nature of the substance.

As of late Tuesday, detectives had canvassed and reviewed hundreds of hours of video and expanded the search area along the Chicago riverfront hoping to find video to be able to release a public description of the offenders.

A dozen police detectives, with the assistance of the FBI, are working the case, the spokesperson said.

Smollett has starred on Fox’s “Empire” since 2015. He plays Jamal, a successful singer in the musical Lyon family. Like his character, Smollett identifies as gay.

In the aftermath of Smollett’s assault, his friends, colleagues and peers showed an outpouring of support for the actor, who is an active advocate for the LGBTQ community.